The present invention relates to the production of phospholes, and to phospholes comprising functional substituents on the phosphorus, these compounds corresponding to the general formula: ##STR2## in which: R.sub.1 and R.sub.2 are identical or different and represent hydrogen or a lower alkyl group of C.sub.1 to C.sub.4 such as a methyl group, and
R.sub.3 represents a group --C.sub.6 H.sub.5, --CH.sub.2 --C.sub.6 H.sub.5, --CH.sub.3, --C.sub.2 H.sub.5, --C.sub.3 H.sub.7 to C.sub.12 C.sub.25 or --(CH.sub.2).sub.n Z where Z denotes a function --COO-alkyl (such as --COOC.sub.2 H.sub.5), --CN, --CO-aryl (such as (--CO--C.sub.6 H.sub.5), --CO-alkyl (such as --CO--CH.sub.3), or --OH and n.gtoreq.1.
Among these compounds, those corresponding to the above formula, in which R.sub.1 and R.sub.2 have the given meaning and R.sub.3 represents --(CH.sub.2).sub.n Z where Z denotes a --COO-alkyl (such as --COOC.sub.2 H.sub.5), --CN, --CO-aryl (such as --CO--C.sub.6 H.sub.5), --CO-alkyl (such as --CO--CH.sub.3) or OH and n.gtoreq.1 with n.noteq.2 for Z=CN, constitute novel industrial products.
The preparation of phospholes is already known by means of the reaction of a dihalogenalkyl or aryl-phosphine with a butadiene whose carbons in the 2 and/or 3 position possibly bear a methyl substituent to obtain a cyclic addition product (called below "cyclic adduct") (see U.S. Pat. Nos. 2,663,736 and 2,663,737 and Chem Abstracts, 497601a-7602c (1955)), then subjecting said adduct to the action of diazobicyclo-undecene (DBU) (see: F. MATHEY and al. Org. Magn. Resonance, 4, 171 (1972) and L. D. QUIN and al. J. Org. Chem., 38, 1858 (1973).
Now, this process of preparation is not devoid of drawbacks resulting from the use of DBU which is an expensive product (which is prepared in three steps and which is difficult to purify and to dry), from the appearance of side-reactions competing with the main reaction, from the practical difficulties of processing the adducts due to the solvent nature of the DBU and finally from the very moderate yields and from the greater or lesser purity of the products obtained.
It is a particular object of the present invention to overcome these drawbacks and more especially to provide phospholes obtainable with good yields and of high purity. The attaining of this objective is all the more advantageous if the needs of industry for these necessitate large amounts having the required purity and at low price.
In other respects, at the present time, very few simple P-functional phospholes have been prepared.
Now, it is also an object of the invention to provide novel phospholes and a process enabling them to be obtaind.